Photo reduction of CO2 to methanol via ZrO2 photocatalyst

Greenhouse gas such as CO2 is the primary cause of global warming. Alternative energy source should be provided without producing more CO2 , such as solar energy. One of the best routes to remedy CO2 is to transform it to hydrocarbons using photo reduction. In our study, CO2 was photocatalytically reduced to produce methanol using a Hg lamp with wavelength 365 nm in a steadystate opticalfiber photo reactor. The opticalfiber photo reactor, comprised of near 120 Cu/ZrO2 coated fibers, was designed and assembled to transmit and spread light uniformly inside reactor. ZrO2 film was coated on optical fiber using dipcoating method. Zirconia and Cu-loaded solutions were prepared by a thermal hydrolysis method. The thickness of Cu/ZrO2 film was 53 nm and consisted of very fine spherical particle with diameter of near 14 nm. The XRD spectra indicated the anatase phase of all ZrO2 and Cu/ZrO2 films. The wavelength of absorption edge was on 367 nm, equivalent to near 3.3 eV. Most active Cu species on ZrO2 surface were Cu2O clusters, and played an important role for the formation of methanol. The methanol yield increased with UV irradiative intensity. Photo activity increased with increasing Cu loadings. Maximum methanol rate was 0.45 μmole/g-cat•hr using 1.2 wt%-Cu/ZrO2 catalyst under 16 W/cm2 irradiation, 1.3 bar pressure of CO2, and 5000 seconds mean residence time. Higher than 1.2 wt% Cu loading gave less rate of methanol yield because of the masking effect of Cu2O clusters on the surface of ZrO2 .

Keywords:

Photo reduction , intensity , optical fiber , photo reactor , catalyst